Heretofore, several patents have disclosed methods and apparatus for monitoring the development of electrostatic images and control of the development process, the relevant portions of which may be briefly summarized as follows:
U.S. Pat. No. 4,868,600 to Hays et al., issued Sep. 19, 1989, and hereby incorporated by reference in its entirety, discloses the rendering of electrostatic images using scavengeless development.
U.S. Pat. No. 5,519,497 to Hubble, III et al., issued May 21, 1996, teaches a closed loop system, which regulates developability by measuring the density of a powder image developed on a photoconductive surface. This is due to the relative stability of the transfer and fusing processes. The use of densitometers for measuring the optical density of black toner particles is indicated as being known. A sensor capable of measuring reflectivity of toner on a photoreceptor surface to enable high toner developed mass per unit area to be controlled is disclosed.
U.S. Pat. No. 6,690,471 to Tandon et al., issued Feb. 10, 2004, and hereby incorporated by reference in its entirety, discloses an improved plural color spectrophotometer for color correction or color calibration and suitable for use in color processing systems.
U.S. Pat. No. 6,792,220 to Randall et al., issued Sep. 14, 2004, teaches a system and method for determining a plurality of calibration curves for a toner concentration sensor, as well as average and composite calibration curves.
U.S. Pat. No. 6,665,425 to Sampath et al., issued Dec. 16, 2003 and hereby incorporated by reference in its entirety, discloses a system and method for automated, image quality based diagnostics and remediation of document processing systems. The disclosure provides for automated diagnosis, prediction and remediation of failures in document processing systems based on an image quality defect analysis in conjunction with a machine/device data analysis. The systems and methods automatically identify image quality problems in document processing systems, such as analog and digital copiers, printers, scanners, facsimiles, and the like by analyzing specific test patterns via techniques such as image processing and pattern recognition.
It is known, as set forth above in U.S. Pat. No. 4,868,600, to use hybrid scavengeless development (HSD) for the development of latent electrostatic images in reprographic and printing systems. HSD developers generally use a set of wires strung across a development nip to enable scavengeless development. These wires are prone for contamination by fibers and debris contaminating the developer housing. Once contaminated with a fiber or piece of debris, a streak defect will often occur during development of the printed image. The defect is caused by the localized alteration of the electrostatic field about the HSD wires, which in turn is reflected as a streak or similar defect in the developed image. This defect would continue to be printed until the customer inspects the printed output and detects the defect. In large runs, this may lead to substantial quantities of defective prints that would be scrapped.
Fiber and other debris related print defects are an unfortunate side effect of the HSD wires. Streaks, caused by fibers caught on the wires, are readily identified by trained observers, and are believed to be objectionable to customers using HSD based print systems. This disclosure describes using an in-line, real-time scanning system to automatically detect streaks or similar development-related defects. Once detected, the output device print engine would stop and signal that the development system, or HSD wires, needs to be serviced. This corrective action could occur via an internal cleaning system, a customer intervention, or a service call.
A system for the automated detection of printing defects in an image output device, comprising: a photoresponsive member upon which a latent electrostatic image is created in response to an input image; a development system for development of the latent electrostatic image on the photoresponsive member with a marking material of at least one color to produce a developed image for transfer to a substrate; a scanning array, disposed adjacent to the photoresponsive member, for receiving light reflected from the surface of the photoresponsive member and the marking material and generating a plurality of scanned image signals representative thereof; and an image comparer for analyzing the scanned image signals to identify defects in the developed image.
In accordance with another embodiment disclosed herein there is provided a method for the automated detection of printing defects in an image output device, comprising the steps of: developing, on a photoresponsive member, in response to a latent electrostatic image, a developed image for transfer to a substrate; scanning the photoresponsive member for at least a portion of the developed image as the photoresponsive member moves relative to a scanning position, to generate a plurality of scanned image signals representative thereof; and analyzing the scanned image signals to identify defects in the developed image.
In accordance with yet another embodiment disclosed herein there is provided A multipurpose imaging device suitable for producing printed output in response to an input, comprising: an input subsystem; a processor and image storage subsystem; an electrophotographic imaging and development subsystem including a photoresponsive member upon which a latent electrostatic image is created in response to an input image; an output and finishing subsystem including a development system for development of the latent electrostatic image on the photoresponsive member with a marking material to produce a developed image for transfer to a substrate; a scanning array, disposed adjacent to the photoresponsive member, for receiving light reflected from the surface of the photoresponsive member and the marking material and generating a plurality of scanned image signals representative thereof; and an image comparer for analyzing the scanned image signals relative to the input image to identify defects in the developed image
One aspect of this disclosure is based on the observation of problems with conventional image output devices, be they reprographic or printing systems—that of a delay in detecting image quality defects until the output pages are reviewed. This aspect is based on the discovery of a technique that alleviates these problems by providing in-line, automated defect detection of developed electrostatic images using scanning devices. This technique can be implemented, for example, by an in-line scanning array suitable for analyzing a developed image relative to the input image being printed.